Estimates of combining ability for vegetative stage cold tolerance in rice

Ninety F₁ rice hybrids were evaluated for combining abilily for low-temperature tolerance at the vegetative growth stage. Evaluation was done by subjecting the plant to 17℃ and 20℃ water temperatures in separate blocks from 20 days afler transplanting to maturity. Combining ability analysis showed the predominance of additive gene action. The Japonica parents viz. Shimokita, K48, SR5204-91-4-1, Stejaree 45, Barkat and K332 were good donors for vegetative stage cold tolerance. The best sca combinations involved both high and low general combiners. Parental performance per se was a good indicator of gca effects of the parents.